CVE-2026-73437

Client traffic interception via unvalidated DHCP replies

Published Sep 15, 2026 · Updated Sep 15, 2026

Insufficient DHCP reply validation in affected Arista EOS releases allows remote attackers to redirect or interrupt client traffic. The DHCP relay agent forwards DHCPOFFER, DHCPACK, and DHCPv6 Relay-Reply packets whose source is not a configured helper or relay destination. Exploitation requires an active IPv4 or IPv6 helper address and network access sufficient to inject replies, enabling malicious client settings, traffic interception, or denial of service.

CVSS severity6.5
Medium
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient DHCP reply validation in affected Arista EOS releases allows remote attackers to redirect or interrupt client traffic. The DHCP relay agent forwards DHCPOFFER, DHCPACK, and DHCPv6 Relay-Reply packets whose source is not a configured helper or relay destination. Exploitation requires an active IPv4 or IPv6 helper address and network access sufficient to inject replies, enabling malicious client settings, traffic interception, or denial of service.

The record

CVE
CVE-2026-73437
Published
Sep 15, 2026
Updated
Sep 15, 2026
Vendor
Arista Networks
Product
Arista EOS
Classifications
CWE-345, T1557.003
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 15, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.33.0 <=4.33.9M changes=[{"at":"4.33.10M","status":"unaffected"}]
  2. Affected versionversion=4.34.0 <=4.34.7.1M changes=[{"at":"4.34.8M","status":"unaffected"}]
  3. Affected versionversion=4.35.0 <=4.35.5M changes=[{"at":"4.35.6M","status":"unaffected"}]
  4. Affected versionversion=4.36.0 <=4.36.1F changes=[{"at":"4.36.2F","status":"unaffected"}]

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Arista Networks · Arista EOSversion=4.33.0 <=4.33.9M changes=[{"at":"4.33.10M","status":"unaffected"}]; version=4.34.0 <=4.34.7.1M changes=[{"at":"4.34.8M","status":"unaffected"}]; version=4.35.0 <=4.35.5M changes=[{"at":"4.35.6M","status":"unaffected"}]; version=4.36.0 <=4.36.1F changes=[{"at":"4.36.2F","status":"unaffected"}]

Published CVSS scores

9.6Arista NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
6.5Arista NetworksCVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:H/SI:H/SA:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-345Insufficient Verification of Data Authenticity
T1557.003Adversary-in-the-Middle: DHCP Spoofing

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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